The present invention relates, in general, to electrosurgical instruments and, more particularly, to a feedback light apparatus and method used in cooperation with an electrosurgical instrument.
The application of heat to treat bleeding wounds dates back to antiquity, with a hot iron being widely applied in medieval times to cauterize battle wounds to stop bleeding. In cauterization, the essential mechanism behind the treatment is using conductive heat transfer from a hot object to raise the temperature of the bleeding tissue sufficiently high to denature the tissue proteins, or heat the blood sufficiently high to cause a thrombus to form.
Coagulation by means of electrosurgery is also accomplished by heating tissue, but the primary mechanism is electrical power dissipation in the affected tissue, rather than heat transfer from an external object. Current flows through the tissue, and is resisted by the tissue. This creates a small envelope of steam around the electrodes of the electrosurgical instrument, and the steam vaporizes the tissue to cause cellular dehydration, denaturation of proteins, and tissue shrinkage, leading to blood vessel thrombosis. This form of hemostasis is now routinely used in both open and endoscopic surgery for small blood vessels (typically smaller than 1 mm), and has largely replaced individual vessel ligation.
Currently-available bipolar grasping instruments for electro-coagulation of tissue, or xe2x80x9ctissue welding,xe2x80x9d generally use only two electrodes of opposite polarity, one of which is located on each of the opposite jaws of the grasper. As illustrated in FIG. 1, in use, tissue is held between a pair of grasper jaws (shown in cross-section) having first and second electrodes (Electrode 1 and Electrode 2) of opposite polarity. Bipolar current flows between the two electrodes along the illustrated current flow lines, with tissue coagulating first at the edges of the jaws. Then, as the tissue dries out and the impedance increases, the current flows through the moister tissue and the coagulation spreads both inward toward the center of the jaws and outward from the jaw edges. The tissue coagulation and heating outside the jaw continues until the power is shut off.
Thermal damage to adjacent structures can occur due to this spread of thermal energy outside the jaws of the instrument. Because of the spread of thermal energy outside the jaws of the instrument, it is difficult to coagulate long sections of tissue, such as bowel, lung, or larger blood vessels, without significant lateral thermal spread. Over-coagulation frequently occurs, resulting in tissue sticking to the jaws of the instrument. When the jaws of the instrument are opened, if the tissue sticking is severe, the tissue can be pulled apart, thus adversely affecting hemostasis. Under-coagulation can occur if insufficient energy has been applied to the tissue, and the resulting hemostasis will be incomplete.
Some electrosurgical devices measure the impedance of tissue to be affected as a feedback parameter to maintain the impedance of the tissue within predetermined limits by controlling the level of electrosurgical energy. By controlling the level of electrosurgical energy applied to a tissue area, the electrosurgical device allows simultaneous cutting and cauterization of tissue independently of a user""s technique.
Other electrosurgical tools have digital display units or bar graph displays for indicating power, voltage and other parameters relating to electrosurgical device operation. Such displays often provide a theoretical value and not a value measured at a relevant tissue area. While these displays might provide some information, actual measurements of the affected tissue are necessary in order to allow a user to most effectively cut and cauterize tissue during an electrosurgical procedure. Furthermore, such graphical displays require a user to focus attention on the display for an amount of time necessary to ascertain a display reading and process that information.
Still other electrosurgical devices provide an audible alarm that sounds when a theoretical energy level is exceeded, thus not providing information from an affected tissue area. Also, as one skilled in the art will appreciate, an audible alarm may be confused with other equipment having sounds associated therewith, such as cardiac and respiratory monitors.
U.S. Pat. No. 5,817,091 filed May 20, 1997 issued Oct. 6, 1998 to Medical Scientific, Inc. discloses an electrosurgical system having a visual indicator. The electrosurgical system further includes a lamp in electrical communication with the active and return electrodes, wherein the neon bulb is illuminated when the current flowing through the tissue exceeds a predetermined threshold.
U.S. Pat. No. 5,762,609 filed Jun. 7, 1995 issued Jun. 9, 1998 to Sextant Medical Corporation discloses a class of surgical tools constructed from the surgical tools and a tissue state monitoring device to assess or image changes in the chemical or structural composition of tissue over time.
U.S. Pat. No. 5,599,350 filed Apr. 3, 1995 issued Feb. 4, 1997 to Ethicon Endo-Surgery discloses an electrosurgical hemostatic instrument in which the coagulation status of tissue engaged by two elements delivering electrosurgical energy to tissue may be observed, and in which damage from thermal spread may be minimized.
U.S. Pat. No. 4,800,878 filed Aug. 26, 1987 issued Jan. 31, 1989 to Becton, Dickinson and Company discloses a disposable electrosurgical knife handle and blade with a built-in warning light positioned on the top of the handle in the surgeon""s line of vision during surgical procedures in order to warn, instantly, of unwanted surges in the electrical system.
U.S. Pat. No. 6,258,085 filed May 11, 1999 issued Jul. 10, 2001 to Sherwood Services AG discloses a method of determining the probability of a patient burn under a return electrode in a monopolar electrode.
U.S. Pat. No. 6,245,065 filed Sep. 10, 1998 issued Jun. 12, 2001 to Scimed Life Systems, Inc. discloses systems and methods for controlling the power supplied to an electrosurgical probe. The systems and methods may be used to monitor electrode-tissue contact, adjust power in response to a loss of contact, and apply power.
Thus, it would be advantageous to provide an electrosurgical tissue welding instrument in which the current pathway is limited to tissue within the jaws, so as to minimize tissue damage due to thermal effects outside the jaws of the device. It would be advantageous to provide an electrosurgical tissue welding instrument which allows coagulation of a relatively long section of tissue, while minimizing the lateral spread of thermal energy. It would be advantageous to provide an electrosurgical tissue welding instrument in which the maximum current density in the coagulated tissue occurs away from the electrodes, and between two stick resistant surfaces, to minimize tissue sticking to the electrodes. It would be advantageous to provide an electrosurgical tissue welding instrument where the current flow is self-limiting to prevent over-coagulation of the tissue. It would be advantageous to provide an electrosurgical tissue welding instrument which provides a clear view of coagulated tissue to prevent under-coagulation of the tissue. It would be advantageous to provide an electrosurgical tissue welding instrument that provides a cutting capability combined with the other features and advantages described above.
The present invention relates, in general, to electrosurgical instruments and, more particularly, to a feedback light apparatus and method used in cooperation with an electrosurgical instrument. The present invention further comprises first and second moveable jaws each comprising a tissue contacting surface in face-to-face relating with the tissue contacting surface of the other jaw, where the tissue contacting surfaces of the jaws comprise an insulating material. A first electrode is housed within the first moveable jaw and a second electrode is housed within the second moveable jaw, where the electrodes are connectable to a power source for providing an electric current between the electrodes. When tissue is grasped between the tissue contacting surfaces, electrical current may be caused to flow between the electrodes and through the tissue grasped between the tissue contacting surfaces forming a first circuit.
The present invention further comprises a feedback light connectable to a first lead and a second lead in order to form a second circuit, where the second circuit is adjacent to the first circuit in order to facilitate capacitive coupling between the first and second circuits in order to light the feedback light. The present invention has application in conventional endoscopic and open surgical instrumentation as well application in robotic-assisted surgery.